The 1918 U.S. National Championships (now known as the US Open) was a tennis tournament that took place on the outdoor grass courts at the West Side Tennis Club, Forest Hills in New York City, United States. The women's tournament was held from June 17 until June 22 while the men's tournament ran from August 26 until September 3. It was the 38th staging of the U.S. National Championships and due to World War I the only Grand Slam tennis event of the year.
See main article: 1918 U.S. National Championships – Men's singles. 
Robert Lindley Murray defeated Bill Tilden 6–3, 6–1, 7–5
See main article: 1918 U.S. National Championships – Women's singles. 
Molla Bjurstedt defeated Eleanor Goss 6–4, 6–3
Bill Tilden / Vincent Richards defeated Fred Alexander / Beals Wright 6–3, 6–4, 3–6, 2–6, 6–4
Marion Zinderstein / Eleonora Sears defeated Molla Bjurstedt / Mrs. Rogge 7–5, 8–6
Hazel Wightman / Irving Wright defeated Molla Bjurstedt / Fred Alexander 6–2, 6–4